fix(generic): honor m tags during realization

filter/generic/generalizer/map.go

@@ -68,7 +68,15 @@ func (g *MapGeneralizer) Realize(obj any, typ reflect.Type) (any, error) {
 		obj = removeClass(obj)
 	}
 	newobj := reflect.New(typ).Interface()
-	err := mapstructure.Decode(obj, newobj)
+	decoder, err := mapstructure.NewDecoder(&mapstructure.DecoderConfig{
+		Result:  newobj,
+		TagName: "m",
+	})
+	if err != nil {
+		return nil, perrors.Errorf("creating map decoder failed, %v", err)
+	}
+
+	err = decoder.Decode(obj)
 	if err != nil {
 		return nil, perrors.Errorf("realizing map failed, %v", err)
 	}

filter/generic/generalizer/map_test.go

@@ -49,6 +49,11 @@ type testPlainObj struct {
 	EeEe int
 }
 
+type testMTagObj struct {
+	UserID string `m:"user_id"`
+	Name   string
+}
+
 func TestObjToMap(t *testing.T) {
 	obj := &testPlainObj{}
 	obj.AaAa = "1"
@@ -71,6 +76,23 @@ func TestObjToMap(t *testing.T) {
 	assert.Equal(t, 100, m["eeEe"].(int))
 }
 
+func TestMTagRoundTrip(t *testing.T) {
+	original := testMTagObj{
+		UserID: "42",
+		Name:   "alice",
+	}
+
+	generalized, err := mockMapGeneralizer.Generalize(original)
+	require.NoError(t, err)
+	generalizedMap, ok := generalized.(map[string]any)
+	require.True(t, ok)
+	assert.Equal(t, "42", generalizedMap["user_id"])
+
+	realized, err := mockMapGeneralizer.Realize(generalized, reflect.TypeOf(original))
+	require.NoError(t, err)
+	assert.Equal(t, original, realized)
+}
+
 type testStruct struct {
 	AaAa string
 	BaBa string `m:"baBa"`